Progress of Technology on Mechanical Design of Steam Turbine Blade in Japan

Abstract

In Japan, the capacity and the efficiency of the steam turbine have been remarkably increased since 1950s. It was the technology on the long last blade of the low pressure steam turbine that made it possible. At present, the longest last blade made of steel in Japan is 50 inch long for 3600 rpm turbine, 74 inch long for 1800 rpm turbine. These long blades have been developed by the own technology of the Japanese turbine maker, and the Japanese technology on the long last blade is leading in the world. The development of the longer last blade requires the cutting-edge technology from the aspect of the fluid dynamics, the material strength, the vibration engineering, and so on, because the longer last blade causes the increase of the steam velocity and the centrifugal force, the decrease of the natural frequency, and so on. This paper describes the history and the prospect on the technology required to develop the last blade of the steam turbine, focusing on the aspect of the mechanical design.